oooh, YES. i LOVE this. your mind. especially if it starts with RoyTim instead of the expected DickRoy or DickTim? that's so good. it's the definition of Roy being a little shit, accidentally seducing Dick's younger brother and sleeping with him. i think it's fun if this specifically highlights Roy's fuckboy era, where he slept with just about anyone and wasn't shy about hiding it, as opposed to him being a bit more mature and careful about sleeping around with Tim, knowing Dick would disapprove. (thinking specifically about the time Roy slept with Helena, Dick's complicated ex situationship and when Dick asked Roy was very casually like "oh dw man i wouldn't get between you two like that, i only slept with her!" and just being so casual about it)
Roy *could* hide it from Dick, and tbh he knows he should. but it's a family full of detectives anyway, so what's the point? Roy can only make up so many excuses for being in Gotham and if Tim is old enough to consent, it's none of Dick's business. even if Roy is sort of rubbing it in his face to *make it* his business. i am delighted by the idea that Roy is almost getting off to how angry Dick is about it. Dick doesn't have a lot of good arguments about why Roy *can't* do this. the "he's basically my baby brother" argument doesn't go very far, and it doesn't seem to be stopping Tim. Tim can pretend to be annoyed and scolding Roy about all the bragging, but Roy sees the hidden smiles.
i think it's also fun if Tim is purposefully doing this to rile Dick up. maybe he and Dick have danced around the idea of feelings, but Dick has always shut down their long stares and lingering touches by saying how Tim is like a brother to him. and so, Tim wants to call his bluff. if he's just Dick's brother, than Dick has no right to get jealous over who Tim does or doesn't like. and Roy is two birds with one stone. not only is he someone for Tim to sleep with to make Dick jealous, Dick's *best friend*, even. but he's someone Tim has genuinely had a thing for, and it's easy for him to play it off as though Roy was the one who came onto him and not Tim making himself obvious bait. he's honestly shocked it's worked as well as it has, with Dick seething every time Tim and Roy are in the same room, even if they're behaving. he lets Roy make the jokes about their sex life and show displays of affection because Tim knows it's building and building for Dick, and eventually, he's going to break.
only Dick went a little too hard on the "brothers" excuse and now it's an excuse sort of believes, which adds a delightful bit of incestual vibes to it. bc Dick tells Tim that he *made his point* a little too late, and now Tim actually likes Roy. so Dick is going to have to explain this to Roy too. and somehow, the awkward conversation leads to Roy suddenly being very interested in an incest kink and seeing exactly how "brotherly" they are-
them all sleeping together is Roy's suggestion, and Tim is *definitely* into the idea, and even Dick is more on board then he expects to be. maybe he and Roy fooled around once when they were kids and it was never thought about beyond a sexuality exploration sort of thing for both of them. but now, Dick has to admit it wouldn't be the *worst* sight to see Roy fuck Tim. after all, Roy has to show Dick how Tim likes it. and Roy is *really* leaning into the brothers thing the whole time.
after the first few times they sleep together, i think Dick would just accept Tim and Roy are a package deal. and of all his friends, Roy really can't be the worst one to date. all the fuckboy stuff stripped away, Roy is a great boyfriend and makes sure Dick and Tim are more than happy. he remembers anniversaries and little "just because" gifts. and he's a great dad, which somehow adds to it all.
anyway yes, i love the potential of these three together with Roy being a Little Shit the entire time just because he can.